The first car I ever owned with rear disks, 1991 Ford Taurus, had the pistons than needed to be turned in. I had never been exposed to that before and ruined a caliper trying to figure out how to compress it. I believe it has something to do with the parking brakes. I'm thinking some, like Chryslers with the drum brake parking brake system inside the rotor, don't need to be turned to compress. I don't know, either way, they have been around for a long time. All the vehicles I own now with 4 wheel disks, Ford, Dodge, Hyundai, Mitsubishi and Honda all need to have the piston turned to compress it.